Merge branch 'development-restricted' into mbedtls-2.22.0r0
Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/ChangeLog b/ChangeLog
index 5d49004..5c4a846 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -13,6 +13,11 @@
legitimate clients, resulting in a Denial of Service. This could only
happen when MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE was enabled in config.h
(which it is by default).
+ * Fix side channel in ECC code that allowed an adversary with access to
+ precise enough timing and memory access information (typically an
+ untrusted operating system attacking a secure enclave) to fully recover
+ an ECDSA private key. Found and reported by Alejandro Cabrera Aldaya,
+ Billy Brumley and Cesar Pereida Garcia. CVE-2020-10932
Bugfix
* Fix compilation failure when both MBEDTLS_SSL_PROTO_DTLS and
diff --git a/library/ecp.c b/library/ecp.c
index ee0a460..d3e42a9 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -2016,6 +2016,20 @@
final_norm:
#endif
+ /*
+ * Knowledge of the jacobian coordinates may leak the last few bits of the
+ * scalar [1], and since our MPI implementation isn't constant-flow,
+ * inversion (used for coordinate normalization) may leak the full value
+ * of its input via side-channels [2].
+ *
+ * [1] https://eprint.iacr.org/2003/191
+ * [2] https://eprint.iacr.org/2020/055
+ *
+ * Avoid the leak by randomizing coordinates before we normalize them.
+ */
+ if( f_rng != 0 )
+ MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, RR, f_rng, p_rng ) );
+
MBEDTLS_ECP_BUDGET( MBEDTLS_ECP_OPS_INV );
MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, RR ) );
@@ -2388,6 +2402,20 @@
MBEDTLS_MPI_CHK( mbedtls_mpi_safe_cond_swap( &R->Z, &RP.Z, b ) );
}
+ /*
+ * Knowledge of the projective coordinates may leak the last few bits of the
+ * scalar [1], and since our MPI implementation isn't constant-flow,
+ * inversion (used for coordinate normalization) may leak the full value
+ * of its input via side-channels [2].
+ *
+ * [1] https://eprint.iacr.org/2003/191
+ * [2] https://eprint.iacr.org/2020/055
+ *
+ * Avoid the leak by randomizing coordinates before we normalize them.
+ */
+ if( f_rng != NULL )
+ MBEDTLS_MPI_CHK( ecp_randomize_mxz( grp, R, f_rng, p_rng ) );
+
MBEDTLS_MPI_CHK( ecp_normalize_mxz( grp, R ) );
cleanup: